The present invention relates to eddy current equipment for braking a vehicle.
Equipment of this type conventionally comprises a portion (stator) that is fixed to the chassis of the vehicle and that includes inductor windings, and a moving portion (rotor) including an armature, and coupled to a rotary element of the vehicle, generally its transmission shaft. In certain eddy current braking equipments to which the invention can also be applied, the inductor windings are carried by the rotor and the armature is carried by the stator (see FR-A-2 667 741, for example).
The term "inductor winding" or more simply "winding" is used herein to cover both an inductor winding proper and a group of such windings that are permanently interconnected in series and/or in parallel. Each winding as defined in this way produces a magnetic field when powered by the vehicle battery.
The armature is a body of ferromagnetic material which, when moving relative to excited windings, has electrical currents known as "eddy" currents induced therein. Because of the resistivity of the armature, these eddy currents cause energy to be dissipated, and this results in the rotor, and thus the vehicle, being slowed down. The energy is dissipated in the form of heat, and the rotor is commonly given a finned configuration suitable for disposing of said heat.
The driver of the vehicle can actuate a multi-position control lever to obtain a braking effect on the vehicle with a torque that varies depending on the position selected for the lever. This variability is obtained by a set of relays each serving to excite one of the windings, with the number of relays in the closed-circuit position depending on the position of the lever. In a typical equipment, there are four inductor windings, and the lever has five positions corresponding respectively to 0, 1, 2, 3, and 4 of the relays being closed, with corresponding proportional braking torques being obtained.
In the above-mentioned application FR-A-2 667 741, there is described a way of determining the braking torque obtained by a brake having a rotary inductor winding, the determination being based on measured variation in the voltage between two points of the stationary armature. That technique is not easily transposable to a brake having a stationary inductor winding and a rotary armature. In addition, since it is based on measuring an effect of the inductor excitation, it does not make it possible to determine the braking torque that would be obtained for a feed setting other than that actually being applied. However, this type of information can be very useful in the context of intelligent management of the various braking resources of the vehicle (electromagnetic brake, disk brakes, engine braking.
An object of the present invention is to provide a brake equipment suitable for providing in simple manner information concerning the actual and/or available braking torque.